The present invention relates to an eyeglass lens processing apparatus for processing a periphery of an eyeglass lens.
In a processing process forming a bevel at a periphery of an eyeglass lens in order to fit the lens into a rim of an eyeglass frame, the shape of the rim is measured three-dimensionally and the 2-D outline shape (two-dimensional outline shape) and the 3-D circumference (three-dimensional circumference) of the rim are obtained based on the measured 3-D shape (three-dimensional shape) of the rim. The obtained 2-D outline shape and the obtained 3-D circumference of the rim are input to an eyeglass lens processing apparatus. In the eyeglass lens processing apparatus, the path of the edge position of the lens chucked and held by a lens chuck shaft is measured based on the input 2-D outline shape and the path of the bevel apex position is obtained based on the measured edge path. The obtained bevel path is corrected (circumference-corrected) so that the 3-D circumference of the bevel path will match the input 3-D circumference, thereby forming the bevel on the periphery of the lens based on the corrected bevel path.
There is a method for obtaining the 2-D outline shape assumed in case the bevel path is obtained as mentioned above, as a projection shape of the rim in its warp direction. With this method, in case a lens with a large lens curve undergoes boxing center chuck processing (processing in which a lens is processed while being chucked and held by the lens chuck shaft at the geometrical center (the boxing center) of the 2-D outline shape) to tailor the lens to a rim with a large warp, a change in the shape caused by warp is small even if the circumference correction is executed on the obtained bevel path, which leads to high-precision processing.
The method for obtaining the 2-D outline shape as the projection shape of the rim in its warp direction is effective in the boxing center chuck processing alone. In case a lens with a large lens curve undergoes optical center chuck processing (processing in which a lens is processed while being chucked and held by a lens chuck shaft at the optical center of the lens), the larger the lens curve of the lens is, or the larger the warp of the rim is, the larger the change in the shape caused by circumference correction becomes. This makes it difficult to perform high-precision processing.
In view of the related art problems, an object of the invention is to provide an eyeglass lens processing apparatus capable of performing high-precision processing even in case a lens with a large lens curve undergoes optical center chuck processing to tailor the lens to a rim with a large warp.